Shafts are provided in underground mines for a variety of reasons including access between levels and ventilation. When they are no longer required for the purpose for which they were provided, their presence becomes problematic. The shaft becomes a safety hazard for people who must work or move under or in the vicinity of the shaft at the lower level because debris is commonly dislodged from the shaft wall and it is possible for objects to fall from the upper level. In many instances it is deemed necessary to seal such shafts by filling them completely with concrete. But it will be readily appreciated that this is a very expensive solution to overcome the safety risk. In other circumstances, closure of the shaft is only required temporarily, and if it has been sealed for safety reasons, the subsequent removal of the sealing material is also an expensive task.
Throughout the specification and claims the term “shaft” shall be taken as a passageway which is provided in a mine or a like environment and which has an inclination generally in excess of 45° and which interconnect two passageways in the forms of tunnels where the tunnels serve to provide access for the passage of personnel along the tunnels.
Shafts are used in mines for the purposes of ventilation and the delivery of materials from the upper tunnel into the lower tunnel. When the shafts are no longer required either permanently or for a period of time, it is desirable that the shaft be closed in order that the danger that the open shaft can present for personnel in the tunnels connected by the shaft is reduced. In this regard it is desirable that the blocking of the shaft be readily reversible and that the shaft be blocked close to the junctions of the shaft with each tunnel that it connects to. Where the shaft connects with a tunnel at or proximate the floor of a tunnel, the blockage of the shaft close to the tunnel ensures that anyone or anything that falls into the shaft will not fall very far and can be readily retrieved from the shaft. In addition, where the shaft connects with a tunnel at or close to the roof of a tunnel, the blockage of the shaft close to the roof minimises the amount of rock material from the walls of the shaft that can fall into the shaft.